The present invention generally relates to the field of material testing and, more particularly, to methods and systems for detecting flaws in structures using vibratory waves.
Testing the health of structures, such as composite-material structures used in aircraft manufacturing, typically has been a time consuming and costly endeavor. To reduce testing time, the aircraft manufacturing industry, for example, has been searching for methods of globally rather than locally testing of aircraft sub-assemblies. A conventional approach used to globally test composite structures requires excitation of a structure with a vibratory wave and monitoring the response of the structure in the frequency domain. This conventional approach typically requires considerable power for exciting the structure and also extensive time for analyzing the response spectrum.
The conventional approach is further complicated by an exhibited property called “acoustoelasticity.” The frequency response of the structure under test may change with a change in strain within the structure. Variables, such as temperature, torque specifications, part orientation, and weight on the structure may change the internal strain of the structure and thus change its frequency response. Using the conventional approach, it is nearly impossible to distinguish a flaw in a structure from a change in internal strain in the structure.